The inventive concept relates to an auxiliary power supply and a user device including the auxiliary power supply. A user device may be or may include a storage device. A user device may be a storage device such as a memory card. Alternatively, a user device may be an electronic device such as a personal computer, a digital camera, a camcorder, or a mobile phone. If a user device is an electronic device, in most cases, the user device may include a storage device for internally storing data.
A user device receives power supplied from an internal or external power supply. However, the user device may be seriously damaged by a sudden power off (SPO) of the power supply. Accordingly, an auxiliary power supply for providing auxiliary power to the user device when an SPO occurs is required.